Computer devices, and especially mobile computer devices such as laptop computers, mobiles telephones, Personal Digital Assistants and so on, may be provided with location software that allows third parties to know the geographical location of the device (and by association, the user of the device).
Taking the example of a mobile device such as a mobile telephone, a location application is run at the mobile device. The location application obtains location information from, for example, a navigation satellite system such as the Global Positioning System (GPS). Other types of location information may be used. For example, the identity of the network cell in which the mobile device is located can provide crude location information to the location application, accurate to within, say, 1 kilometer. Alternatively, the identity of an Access Point (AP) to a Wireless Local Area Network (W-LAN) can also be used to provide crude location information to the location application.
Once the location application has obtained the location information, the location information is made available to third parties. This may be publicly available or restricted to a group of users known to the mobile device user. For example, Alice has a mobile device that has a location application installed on it. The location application uses GPS to find location information. When Alice's location application is turned on, the location application obtains GPS data and keeps an accurate record of Alice's geographical location. Bob is one of Alice's friends, and wishes to know where Alice is, so Bob uses his mobile device to communicate with Alice's mobile device, and the location application provides Alice's geographical information to Bob's device.
There are some circumstances in which Alice may not wish Bob to know where she is, although she wishes to maintain the appearance that her location application is reporting her location. For example, if Alice is a freelance worker, she may work for several different companies, who may be competitors. In this case, Alice may not wish third parties to know where she is, how long she is spending with her clients, and so on. However, she may still wish to use other functionality of the location application, for example a map function. It would be desirable to allow a user to run a location application in a “privacy mode”; a mode in which the location application is active, but does not report the real geographical location of the device to third parties.